# Number System Questions for RRB Group-D Set-2 PDF

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## Number System Questions for RRB Group-D Set-2 PDF

Download Top-14 RRB Group-D Number System Questions set-2 PDF. RRB GROUP-D Maths questions based on asked questions in previous exam papers very important for the Railway Group-D exam.

Question 1: What is the Lowest Common Factor of 81, 108 and 210?

a) 1

b) 3

c) 7

d) 9

Question 2: What is the HCF of 90, 135, 210?

a) 3

b) 6

c) 9

d) 15

Question 3: x and y are the smallest two digit prime numbers such that x = 2y + 1. What is the value of x – y?

a) 12

b) 18

c) 24

d) 30

Question 4: What is the LCM of $7^5*8^6$, $7^3*8^4*9^2$ and $7^4*8^5*9$?

a) $7^3*8^4$

b) $7^3*8^4*9^3$

c) $7^5*8^6*9^2$

d) $7^6*8^7*9^3$

Question 5: What is HCF of 195, 390, 312 and 702?

a) 7

b) 13

c) 39

d) 65

Question 6: Which is the smallest number which when divided by 5,6 and 7 leaves a remainder of 2?

a) 212

b) 262

c) 282

d) 302

Question 7: Which of the following is NOT a prime number?

a) 43

b) 53

c) 71

d) 91

Question 8: If the square root of 5.44802281 is 2.3341, what is the square root of 5448022.81?

a) 23341.1

b) 2334.1

c) 233.41

d) 23.341

Question 9: What is the HCF of 28, 42 and 56?

a) 0

b) 1

c) 7

d) None of the above

Question 10: What is the LCM of $3^2 * 2^3$, $4^2 * 3 * 2$ and $3^3 * 2 ^4$?

a) 864

b) 5184

c) 7776

d) 3888

Question 11: What is the Highest common factor of: 391, 483, 943 and 253?

a) 17

b) 19

c) 21

d) 23

Question 12: What is the range of the following numbers?
19, 23, 17, 25, 18, 20, 20, 31, 16

a) 15

b) 18

c) 20

d) 22

Question 13: If 9765X is divisible by 11, what is the value of X?

a) 1

b) 3

c) 4

d) 8

Question 14: Which of the following numbers is NOT a multiple of 225?
2025, 2925, 5675, 6975

a) 2025

b) 2925

c) 5675

d) 6975

The lowest common factor of any set of natural numbers is 1. The Highest Common Factor of these three numbers is 3.

90 = 3 * 3 * 2 * 5
135 = 5 * 3 * 3 * 3
210 = 2 * 5 * 3 * 7
So, 3 * 5 is the common factor of the three numbers.

Since we are interested in the smallest two digit prime numbers, let’s start with the number 11.
If y = 11, x = 2 * 11 + 1 = 23, which is also a prime number.
So, the (x,y) set (23,11) satisfies the condition of 1) Prime numbers 2) Two digits 3) x = 2y + 1. So, the required answer is x – y = 23 – 11 = 12

The numbers are $7^5*8^6$, $7^3*8^4*9^2$ and $7^4*8^5*9$.
Since, 7, 8, 9 are relatively prime, LCM of the given three numbers will contain the highest powers of 7,8,9 from all the given numbers.
Highest power of 7 is 5
Highest power of 8 is 6
Highest power of 9 is 2
So, LCM =$7^5*8^6*9^2$

195 = 39 * 5
390 = 39 * 10
312 = 39 * 8
702 = 39 * 18
So, the HCF is 39

The number is the LCM of 5,6 and 7 plus 2
So, 5 * 6 * 7 = 210 + 2 = 212

91 = 7 * 13

5448022.81 = 5.44802281 * $10^6$
So, $\sqrt{5.44802281 * 10^6}$ = 2.3341 * 1000 = 2334.1

14 * 2 = 28
14 * 3 = 42
14 * 4 = 56
So, the Highest Common Factor of 28, 42 and 56 is 14.

The numbers can be arranged as 3 * 24, 4 * 24, 18 * 24
So, 24 is common in all the three numbers.
So, the LCM = LCM( 3 , 4 ,18 ) * 24 = 36 * 24 = 864

23 * 11 = 253
23 * 17 = 391
23 * 21 = 483
23 * 41 = 943

So, the HCF of the given numbers is 23

The range of the numbers is given by the largest number – the smallest number = 31 – 16 = 15